Pouch-type secondary battery

ABSTRACT

A pouch-type secondary battery including: an electrode assembly comprising a positive electrode plate, a negative electrode plate and a separator; a negative electrode tab electrically connected to the negative electrode plate and having a first tab tape; and a positive electrode tab electrically connected to the positive electrode plate and having a second tab tape wherein one or two of end portions which the positive electrode tab crosses are located inside a sealing portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/196,167, entitled “POUCH-TYPE SECONDARY BATTERY” and filed Aug. 2,2011, which is a continuation of U.S. application Ser. No. 12/036,006,filed on Feb. 22, 2008, now U.S. Pat. No. 8,034,481, issued Oct. 11,2011, which claims priority to and the benefit of Korean PatentApplication No. 10-2007-0049249, filed May 21, 2007 in the KoreanIntellectual Property Office, the entire content of each of which isincorporated by reference herein.

BACKGROUND

1. Technical Field

The present disclosure relates a pouch-type secondary batter, and moreparticularly, to a pouch-type secondary battery exhibiting reducedswelling and corrosion of a cladding.

2. Description of the Related Art

As a portable electronic devices such as video cameras, portable phones,and portable computers become lighter while increasing performance,research is active on secondary batteries used as their power sources.Examples of suitable secondary batteries include nickel-cadmiumbatteries, nickel-hydride batteries, nickel-zinc batteries, and lithiumsecondary batteries.

Of these types of secondary batteries, lithium secondary batteries arewidely used in many industrial fields because of small size, highcapacity, high operating voltages, and excellent energy densities perunit weight. Lithium secondary batteries are classified according to thetype of electrolyte as lithium ion batteries using a liquid electrolyte,and lithium polymer batteries using a polymer electrolyte.

Lithium secondary batteries are also classified according to the shapeof the can into which the electrode assembly is inserted intocylinder-type, prism-type, and pouch-type batteries. A pouch-typesecondary battery comprises a pouch cladding, which typically has amulti-layer structure comprising a metal foil layer and resin layerscoated on top and bottom surfaces of the metal foil layer. Thus, thepouch-type is typically much lighter in weight than the cylindrical typeor the prism type. Accordingly, it is possible to significantly reducethe weight of a secondary battery and to provide a variety of shapesusing a pouch-type secondary battery.

A typical pouch-type secondary battery comprises an upper cladding and alower cladding, formed, for example, by folding a rectangular claddinglongitudinally. The lower cladding has a space formed therein by, forexample, press processing. The space in the lower cladding accommodatesan electrode assembly in a “jelly roll” form in which a sandwich of apositive electrode plate, a separator and a negative electrode plate isrolled-up. In a sealed pouch-type secondary battery, edges of the lowercladding are sealed to corresponding edges of the upper cladding aresealed to each other and the package pressurized.

Electrode tabs for providing an electrical connection with an externaldevice are formed in the positive electrode plate and the negativeelectrode plate of the electrode assembly. The electrode tabs protrudefrom the electrode assembly axially relative to the winding axis of thejelly roll, and through a side of the sealed cladding. The electrodetabs are typically aluminum, copper, or nickel, with a thickness andsize sufficient to serve as a current path without a large voltage drop.

In order to improve adhesion between a polymer layer inside the claddingand the electrode tab, the surface of the polymer layer may contain anadhesive, or an adhesive tape may be attached to the portion of theelectrode tab that overlaps the cladding.

When thermally fusing the upper and lower claddings to each other, ifthe temperature and pressure are excessively high, or if fused too long,the polymer layer inside the cladding may be pushed out or get damaged,thereby causing a short circuit between the electrode tab and the metalfoil of the cladding. If a short circuit occurs between the electrodetab and the metal foil, the battery discharges between the two electrodetabs through the metal foil, resulting in overheating and/or swelling,and thereby lowering the manufacturing yield. If a short circuit occursbetween the negative electrode tab and the metal foil of the cladding,biasing the metal foil to a negative potential. At a metal corrosionpotential of less than about 1 volt, corrosion of the metal foil occurs.

As a result, as a sealing capability of the cladding is degraded, anorganic electrolyte in the electrode assembly may be evaporated, andexternal humidity and oxygen penetrates the cladding, generating gastherein causing swelling of the cladding.

SUMMARY OF THE INVENTION

Some embodiments provide a pouch-type secondary battery in whichcorrosion and swelling of the cladding are prevented by intentionallyshort-circuiting a metal layer of the cladding with the positiveelectrode tab.

Some embodiments provide a pouch-type secondary battery, comprising: anelectrode assembly comprising a positive electrode plate, a negativeelectrode plate and a separator; a negative electrode tab electricallyconnected to the negative electrode plate and having a first tab tape;and a positive electrode tab electrically connected to the positiveelectrode plate and having a second tab tape wherein one or two of endportions which the positive electrode tab crosses are located inside asealing portion.

Other embodiments provide a pouch-type secondary battery, comprising: anelectrode assembly comprising a positive electrode plate, a negativeelectrode plate and a separator; a cladding accommodating the electrodeassembly; a negative electrode tab electrically connected to thenegative electrode plate and having a first tab tape; and a positiveelectrode tab electrically connected to the positive electrode plate andhaving a second tab tape having the thinner thickness than the first tabtape.

The second tab tape is made of a softer material than the first tabtape.

The cladding comprises a metal layer made of a metal; a thermal fusinglayer formed on one side of the metal layer; and an insulating layerformed on the opposite side of the metal layer to the thermal fusinglayer.

The metal layer is in a state of being electrically connected to thepositive electrode tab.

Some embodiments provide a pouch-type secondary battery, comprising: acladding comprising a sealing portion; an electrode assembly comprisinga positive electrode plate, a negative electrode plate, and a separator,wherein the electrode assembly is disposed in the cladding; a negativeelectrode tab electrically coupled to the negative electrode plate andextending out of the cladding through the sealing portion; a positiveelectrode tab electrically coupled to the positive electrode plate andextending out of the cladding through the sealing portion; a first tabtape disposed between the negative electrode tab and the sealingportion; and a second tab tape disposed between the positive electrodetab and the sealing portion, wherein the second tab tape comprises afirst end distal to the electrode assembly and a second end proximal tothe electrode assembly, and at least one of the first end and the secondend of the second tab tape is located inside the sealing portion.

In some embodiments, the cladding comprises: an upper cladding; and alower cladding comprising a space dimensioned to receive the electrodeassembly, wherein the upper cladding and lower cladding share an edge.

In some embodiments, the sealing portion comprises: an upper sealingportion disposed on an edge of the upper cladding; and a lower sealingportion disposed on an edge of the lower cladding.

In some embodiments, the cladding comprises: a thermal fusing layer; aninsulating layer; and a metal layer disposed between the thermal fusinglayer and the insulating layer. In some embodiments, the metal layer iselectrically coupled to the positive electrode tab. In some embodiments,the metal layer comprises an aluminum-based material. In someembodiments, the thermal fusing layer comprises cast polypropylene(CPP).

In some embodiments, the second tab tape comprises a softer materialthan the first tab tape. In some embodiments, the second tab tape isthinner than the first tab tape. In some embodiments, the second tabtape comprises a material having a lower fusing point than the first tabtape.

In some embodiments, the positive electrode tab is thicker than thenegative electrode tab. In some embodiments, a sum of a thickness of thepositive electrode tab and a thickness of the second tab tape is aboutequal to a sum of a thickness of the negative electrode tab and athickness of the first tab tape.

Some embodiments provide a pouch-type secondary battery, comprising: anelectrode assembly comprising a positive electrode plate, a negativeelectrode plate, and a separator; a cladding receiving the electrodeassembly; a negative electrode tab electrically coupled to the negativeelectrode plate; a first tab tape disposed on the negative electrodetab; a positive electrode tab electrically coupled to the positiveelectrode plate; and a second tab tape disposed on the positiveelectrode, wherein the second tab tape is thinner than the first tabtape.

In some embodiments, the cladding comprises: an upper cladding having anupper sealing portion disposed on an edge thereof; and a lower claddinghaving a lower sealing portion disposed on an edge thereof, wherein thelower cladding comprises a space for accommodating the electrodeassembly.

In some embodiments, the cladding comprises: a metal layer comprising afirst side and a second side; a thermal fusing layer formed on the firstside of the metal layer; and an insulating layer formed on the secondside of the metal layer. In some embodiments, the metal layer iselectrically coupled to the positive electrode tab. In some embodiments,the metal layer comprises an aluminum-based material. In someembodiments, the thermal fusing layer comprises cast polypropylene(CPP).

In some embodiments, the second tab tape comprises a softer materialthan the first tab tape. In some embodiments, the second tab tapecomprises a material having a lower fusing point than the first tabtape.

In some embodiments, the positive electrode tab is thicker than thenegative electrode tab. In some embodiments, a sum of a thickness of thepositive electrode tab and a thickness of the second tab tape is aboutequal to a sum of a thickness of the negative electrode tab and athickness of the first tab tape.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages will become more apparent tothose of ordinary skill in the art by describing in detail preferredembodiments thereof with reference to the attached drawings in which:

FIG. 1 a is an exploded perspective view illustrating a pouch-typesecondary battery according to a first exemplary embodiment;

FIG. 1 b is a top view illustrating an assembled pouch-type secondarybattery according to the first exemplary embodiment;

FIG. 1 c is a side cross-sectional view illustrating a positiveelectrode tab portion of the pouch-type secondary battery according tothe first exemplary embodiment;

FIG. 2 a is a top view illustrating an assembled pouch-type secondarybattery according to a second exemplary embodiment;

FIG. 2 b is a side cross-sectional view illustrating a positiveelectrode tab portion of the pouch-type secondary battery according tothe second exemplary embodiment;

FIG. 3 a is a top view illustrating an assembled pouch-type secondarybattery according to a third exemplary embodiment;

FIG. 3 b is a side cross-sectional view illustrating a positiveelectrode tab portion of the pouch-type secondary battery according tothe third exemplary embodiment;

FIG. 4 a is an exploded perspective view illustrating a pouch-typesecondary battery according to a fourth exemplary embodiment; and

FIG. 4 b is front view illustrating the pouch-type secondary batteryaccording to the fourth exemplary embodiment.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

Exemplary embodiments will now be described more fully hereinafter withreference to the accompanying drawings. In the drawings, the thicknessof layers and regions are exaggerated for clarity. Like numbers refer tolike elements throughout the specification.

FIG. 1 a is an exploded perspective view illustrating a pouch-typesecondary battery according to a first exemplary embodiment. FIG. 1 b isa top view illustrating an assembled pouch-type secondary batteryaccording to the first exemplary embodiment. FIG. 1 c is a sidecross-sectional view illustrating a positive electrode tab portion ofthe pouch-type secondary battery according to the first exemplaryembodiment.

Referring to FIGS. 1 a to 1 c, the illustrated pouch-type secondarybattery in a bare cell form comprises an electrode assembly 400 sealedin a cladding 300, which comprises upper and lower claddings 100 and200.

In other embodiments, in the pouch-type secondary battery has a corepack form in which a printed circuit board comprising safety elements,for example, a protection circuit, a PTC element, and/or a thermistor,is electrically coupled the secondary battery and a protection circuitboard, thereby preventing accidents caused by abnormal operation of thebattery, such as overheating, overcharging, and overdischarging. Someembodiments further comprise a metal case for protecting an appearanceof the pouch-type secondary battery core pack.

In the illustrated embodiment, the lower and upper claddings 100 and 200share a common edge, while the other edges are open to receive theelectrode assembly 400.

A space 210 dimensioned and configured for accommodating the electrodeassembly 400 is formed in either or both of the upper and lowercladdings 100 and 200 by any suitable means, for example, by pressprocessing. In the illustrated embodiment, the space 210 is formed inthe lower cladding 200. A lower sealing portion 220 is formed on edgesof the lower cladding 200, and serves as a sealing surface for sealingthe space 210 by thermal fusing. An upper sealing portion 120 is formedon the upper cladding 100, corresponding to the lower sealing portion220.

The cladding 300 has a multi-layer structure comprised of a thermalfusing layer 310, which has thermal fusing characteristics to serve as asealant, a metal layer 320, which provides mechanical strength andserves as a barrier layer against humidity and oxygen, and an insulatinglayer 330. The thermal fusing layer 310 is formed on one side of themetal layer 320, and the insulating layer 330 is formed on the oppositeside of the metal layer 320. The metal layer 320 comprises any suitablematerial, for example, aluminum, steel, stainless steel, or the like.The thermal fusing layer 310 comprises cast polypropylene (CPP) or thelike. The insulating layer 330 comprises polyethylene terephthalate(PET), nylon, or the like.

The electrode assembly 400 comprises a sandwich of a positive electrodeplate 410, a negative electrode plate 420, and a separator 430 wound ina jelly role form. The positive electrode plate 410 has a positiveactive material coated thereon, and the negative electrode plate 420 hasa negative active material coated thereon. The separator 430 isinterposed between the positive and negative electrode plates 410 and420 to insulate them. The positive electrode plate 410 may be made ofaluminum. A positive electrode tab 415 extends axially from one side ofthe positive electrode plate 410 relative to the axis in which the jellyroll is wound. The negative electrode plate 420 may be made of nickel(Ni). A negative electrode tab 425 extends axially from one side of thenegative electrode plate 420 relative to the axis in which the jellyroll is wound.

Adhesive tab tapes 510 and 520 are disposed on the portions of thepositive and negative tabs 415 and 425 that overlap the sealing portions120 and 220. Preferably, the tab tape 510 formed on the positiveelectrode tab 415 differs from the tab tape 520 formed on the negativeelectrode tab 425 such that the positive electrode tab 415 may be easilyshort-circuited with the metal layer 320 of the cladding when the upperand lower sealing portions 120 and 220 are thermally fused to eachother.

In a detail illustrated in region A in FIGS. 1 b and 1 c, the tab tape510 of the positive electrode tab 415 comprises an end portion 511distal to the electrode assembly 400 that does not extend to the outwardedges of the sealing portions 120 and 220, that is, is recessed from theouter edge of the sealing portions 120 and 220, and as such, does notcompletely isolate the tab 415 from the sealing portions 120 and 220. Inthe case of the tab tape 520 of the negative electrode tab 425, an endportion 521 protrudes from the sealing portions 120 and 220, therebyisolating the negative electrode tab 425 from the sealing portions 120and 220.

Therefore, the tab tape 520 of the negative electrode tab 425 wraps thenegative electrode tab 425 such that the negative electrode tab 425 willnot be short-circuited with the sealing portions 120 and 220, whereas asin region A, the positive electrode tab 415 and the sealing portions 120and 220 are directly thermally fused to each other without interventionof the tab tape 510 so that the positive electrode tab 415 and the metallayer of the sealing portions 120 and 220 are short-circuited.

Since the positive electrode tab 415 is short-circuited with the metallayer of the sealing portions 120 and 220, the metal layer does notreach a corrosion potential of less than about 1 volt, therebypreventing corrosion and swelling in the cladding.

The tab tape 510 of the positive electrode tab 415 preferably comprisesa material that is softer and/or has a lower fusing point than the tabtape 520 of the negative electrode tab 525 so that the tab tape 510 canbe fused faster, thereby more easily short-circuiting the positiveelectrode tab 415.

FIGS. 2 a and 2 b are a top view and a side cross-sectional viewillustrating an assembled state of a pouch-type secondary batteryaccording to a second exemplary embodiment, respectively. In FIGS. 2 aand 2 b and FIGS. 1 a to 1 c, like reference numerals (e.g., 120, 220,400, 415, 425, and 520) denote like parts, and thus detaileddescriptions of those parts are omitted.

Referring to region B of FIGS. 2 a and 2 b, for a tab tape 510′ disposedon the positive electrode tab 415, an end portion 513 of the tab tape510′ proximal to the electrode assembly 400 terminates inside thesealing portions 120 and 220, that is, is recessed from the inner edgesof the sealing portions 120 and 220. For a tab tape 520 disposed on thenegative electrode tab 425, an end portion 523 proximal to the electrodeassembly 400 extends outside the sealing portions 120 and 220. The tabtape 520 disposed on the negative electrode tab 425 wraps the negativeelectrode tab 425 so that the negative electrode tab 425 is notshort-circuited with the sealing portions 120 and 220, whereas as in aregion B, the positive electrode tab 415 and the sealing portions 120and 220 are directly thermally fused to each other without interventionof the tab tape 510′ so that the positive electrode tab 415 and themetal layer of the sealing portions 120 and 220 are short-circuited.Since the positive electrode tab 415 is short-circuited with the metallayer of the sealing portions 120 and 220, the metal layer does notreach a corrosion potential of less than about 1 volt, therebypreventing corrosion and swelling in the cladding.

The tab tape 510′ of the positive electrode tab 415 preferably comprisesa material that is softer and/or has a lower fusing point than the tabtape 520 of the negative electrode tab 425 so that the tab tape 510 canbe fused faster, thereby more easily short-circuiting the positiveelectrode tab 415.

FIGS. 3 a and 3 b are a top view and a side cross-sectional viewillustrating an assembled state of a pouch-type secondary batteryaccording to a third exemplary embodiment, respectively. In FIGS. 3 aand 3 b and FIGS. 1 a to 1 c, like reference numerals (e.g., 120, 220,400, 425, and 530) denote like parts, and thus detailed descriptions ofthose parts are omitted.

Referring to FIGS. 3 a and 3 b, in the case of a tab tape 510″ disposedon the positive electrode tab 415, an end portion 515 distal from theelectrode assembly and an end portion 517 proximal to the electrodeassembly 400 are located inside of, are recessed within, and/or do notextend outside of the sealing portions 120 and 220, as shown in regionsC and D in FIGS. 3 a and 3 b.

In contrast, in the case of a tab tape 520 disposed on the negativeelectrode tab 425, an end portion 525 distal of the electrode assemblyand an end portion 527 proximal to the electrode assembly 400 extend outof the sealing portions 120 and 220.

The tab tape 520 disposed on the negative electrode tab 425 wraps aroundthe negative electrode tab 425 such that the negative electrode tab 425does not short-circuit with the sealing portions 120 and 220, whereas asin regions C and D, the positive electrode tab 415 and the sealingportions 120 and 220 are directly fused without intervention of the tabtape 510″ so that the positive electrode tab 415 and the metal layer ofthe sealing portions 120 and 220 are short-circuited. Since the positiveelectrode tab 415 is short-circuited with the metal layer of the sealingportions 120 and 220, the metal layer does not reach a corrosionpotential of less than about 1 volt, thereby preventing corrosion of thecladding and swelling.

The tab tape 510″ of the positive electrode tab 415 preferably comprisesa material that is softer and/or has a lower fusing point than the tabtape 520 of the negative electrode tab 425 so that the tab tape 510 canbe fused faster, thereby more easily short-circuiting the positiveelectrode tab 415.

That is, according to the first to third exemplary embodiments, of thetwo edges of the tab tape wrapped around the positive electrode tab, oneor both edges are recessed within or located inside the sealing portionsof the cladding so that the positive electrode tab and the sealingportions can be fused to each other without intervention of the tab tapeand the positive electrode tab and the metal layer of the sealingportions can be easily short-circuited. Accordingly, since the positiveelectrode tab is short-circuited with the metal layer of the sealingportions, the metal layer does not reach a corrosion potential of lessthan about 1 volt, thereby preventing corrosion and swelling in thecladding.

FIGS. 4 a and 4 b are an exploded perspective view and a front viewillustrating a pouch-type secondary battery according to a fourthexemplary embodiment. In FIGS. 4 a and 4 b and FIGS. 1 a to 1 c, likereference numerals (e.g., 100 to 430) denote like parts, and thusdetailed descriptions thereof are omitted.

Adhesive tab tapes 710 and 720 are arranged on portions of a positiveelectrode tab 615 protruding from the positive electrode plate 410 and anegative electrode tab 625 protruding from the negative electrode plate420 that overlap the sealing portions 120 and 220. The tab tape 710 ofthe positive electrode tab 615 is thinner than the tab tape 720 of thenegative electrode tab 625. When the sealing portions 120 and 220 arefused at a predetermined temperature and pressure, the thinner tab tape710 is damaged, thereby short-circuiting the positive electrode tab 615to the metal layer 320 of the cladding. When the positive electrode tab615 and the metal layer 320 of the sealing portions 120 and 220 areshort-circuited, the metal layer 320 does not reach a corrosionpotential of less than about 1 volt, thereby preventing corrosion of thecladding and swelling.

In the illustrated embodiment, the positive electrode tab 615, havingthe relatively thinner tab tape 710, is relatively thicker than thenegative electrode tab 625, having the relatively thicker tab tape 720.A sum of the thicknesses of the positive electrode tab 615 and the tabtape 710 is about equal to a sum of the thicknesses of the positiveelectrode tab 625 and the tab tape 720. Accordingly, a problem of thesealing portions not fusing well because of different thickness at thepositions of the tabs is solved.

The fourth exemplary embodiment has been described independently on thefirst to third exemplary embodiments, but the fourth exemplaryembodiment can be applied to any of the first to third exemplaryembodiments.

As described above, it is possible to prevent the metal layer of thecladding from corrosion and to prevent swelling caused by gas generatedin the cladding.

1. A pouch-type secondary battery, comprising: a cladding comprising asealing portion; a electrode assembly comprising a first electrode platehaving a first polarity and a second electrode plate having a secondpolarity different from the first polarity; a first electrode tabelectrically connected to one of the first electrode plate and thesecond electrode plate; a first insulating member surrounding the firstelectrode tab; a second electrode tab electrically connected to theother one of the first electrode plate and the second electrode plate;and a second insulating member surrounding the second electrode tab,wherein the first electrode tab and the second electrode tab extend outof the cladding through the sealing portion, wherein the secondinsulating member is shorter than the first insulating member, andwherein the cladding is formed of a metal layer electrically connectedto the second tab in the sealing portion.
 2. The pouch-type secondarybattery of claim 1, wherein the second insulating member comprises afirst end distal to the electrode assembly and a second end proximal tothe electrode assembly, and wherein at least one of the first end andthe second end of the second insulating member is located inside of thesealing portion.
 3. The pouch-type secondary battery of claim 1, whereinall of the second insulating member is located inside the sealingportion.
 4. The pouch-type secondary battery of claim 1, wherein thecladding further comprises a thermal fusing layer and an insulatinglayer, wherein the metal layer is formed between the thermal fusinglayer and the insulating layer.
 5. The pouch-type secondary battery ofclaim 1, wherein the metal layer is formed of an aluminum-basedmaterial.
 6. The pouch-type secondary battery of claim 1, wherein thefirst insulating member extends through the sealing portion.
 7. Thepouch-type secondary battery of claim 1, wherein the second insulatingmember is thinner than the first insulating member.
 8. The pouch-typesecondary battery of claim 1, wherein the second electrode tab isthicker than the first electrode tab.
 9. The pouch-type secondarybattery of claim 1, wherein the second insulating member is formed of amaterial having a lower fusing point than the first insulating member sothat the second insulating member is fused faster than the firstinsulating member.